1. Field of the Invention
The present invention relates to the field of embryo implantation into the endometrial lining of the uterus of an in-vitro fertilized (IVF) embryo. More particularly to an implantation method using a novel microcatheter, with a shaped tip, capable of both forming a pocket in the uterine wall and transferring an embryo into the pocket. To aid the movement of the microcatheter to the implantation site, a hybrid endoscope insertion arm has been developed with a flexible free end extending seamlessly from a rigid base section.
2. Description of the Related Arts
Improving the success of IVF depends on many factors, one of which is the delivery or transfer of the embryo to the endometrial lining of the uterus and the successful implantation of the embryo therein. It is well known in the art that assisting an embryo to adhere to, or implant within, a pre-determined area of the endometrial lining of the uterine wall, as opposed to simply releasing the embryo into the uterus, will enhance the success of IVF.
One method of assisted embryo transfer is found in U.S. Pat. No. 6,010,448 to Thompson in which an embryo is transferred with the aid of an endoscopic device, via a flexible catheter, to the endometrial lining and affixed thereto with an adhesive.
Another method of embryo transfer is taught in U.S. Pat. No. 5,360,389 to Chenette in which, after using pressurized CO2 gas to distend the uterine walls, an endoscope is used to select an implantation site. A catheter is then used to forcibly inject the embryos into the endometrial lining.
While the embryo transfer methods of these prior art types may be generally satisfactory for their intended purposes, implantation problems can arise in which the trauma to the delicate embryos by either an injection or xe2x80x9cadhesionxe2x80x9d may yield less than optimal solutions and fail to achieve high IVF success rates. Accordingly, a minimally invasive embryo transfer method, which uses a specially formed microcatheter to gently deliver one or more selected embryos into a pocket formed within the endometrial lining would be desirable.
It is an object of this invention to provide a simple gentle method for embryo transfer and implantation. To accomplish this gentle transfer, an improved microcatheter with an angled tip has been developed. This microcatheter is able to work as both a microsurgical instrument, used to form an embryo-receiving pocket within the endometrial lining, and as the vehicle for transferring an embryo into the pocket. It has been observed that by gently securing an embryo within a pocket of endometrial lining, many of the risks of IVF, such as a tubal pregnancy, misplacement of the embryo, and loss of the embryo can be minimized.
Another benefit of actively implanting the embryo within the endometrial lining is derived from the fact that older embryos are used, thus providing for a longer period of observation which allows the most viable embryos to be selected. Higher accuracy in selecting the most viable older embryos yield the additional benefit that fewer embryos need to be implanted to assure a viable pregnancy, thereby minimizing the risk of high-order multiple births associated with those common IVF methods which place larger quantities of less mature embryos within the uterus. See, article by Doug Brunk in Ob.Gyn.News (Volume 35, number 23 at page 1-3) entitled: xe2x80x9cBlastocyst Transfer Cuts Multiples Riskxe2x80x9d.
The within method preferably uses direct visualization of the implantation procedure through an endoscopic device. To enhance the field of vision of the endoscope and to increase the maneuverability of the endoscope within the uterus, the uterine walls may be distended by pressurizing the uterus with an inert, harmless gas such as N2 gas. Other gases may also work, however, the use of pure CO2 gas is contraindicated because of toxicity. Gynecologic and Obstetric Investigation, Volume 43 (2) at pages 73-5, 1997, entitled: xe2x80x9cAssisted implantation: direct intraendometrial embryo transfer.xe2x80x9d This article explains that the introduction of CO2 gas into the uterus to distend the uterine wall and improve endoscopic viewing, (such as that claimed in U.S. Pat. No. 5,360,389), also raises the risk of acidifying the endometrial lining and therefore reduces the viability of the implanted embryo. Moreover, mixtures of CO2 and atmospheric air are not safe because of concern over fatal air embolism.
To enhance the positioning of the microcatheter at the implantation site, a hysteroscope, which is an endoscopic device for intrauterine use, is used. The endoscope both provides direct visualization within the uterus and acts as a guide and support for the microcatheter.